If you're planning on riding your ATV over a large network of trails, you will probably want to camp out overnight so you can get up early the next day and just continue the fun on your ATV.
Most trails allow camping off the ATV trails or have designated campsites at the very least. This allows you to ride the longer, more involved ATV trails and not have to hurry and try to be done riding by sunset. You can enjoy the ride with your buddies, pull over when you've had a day's worth of fun riding your ATVs.
Taking a long weekend to explore the trails is not only relaxing, it makes for a safer ATV ride. You aren't tired, you aren't rushed and you can take your time and really see the area you're riding and you won't have to hurry and be done or only go up a few miles on the ATV trails before having to loop around and come back as many ATV trails don't allow any riding after sundown, even if you have headlights on your ATV.
It also means you can have a great night with your friends after the ride and enjoy a meal by a campfire and make some great memories. A good rule of thumb if you're going to be camping is to follow the "Leave No Trace" standards and basically, if you bring it in, bring it out with you. There should be no trace of your campsite when you and your ATV buddies leave. This applies to campfires too, make sure after the fire is absolutely doused, to scatter the ashes and make sure there is no trace of your having been there.
If you've been thinking of doing something a little different with your buddies when you ride your ATVs, consider taking an extended weekend with your friends and it an overnight stay so you can hop on your ATVs the next day and continue the fun!